Ozone perturbation experiments in a two‐dimensional circulation model

A two‐dimensional circulation model is used to investigate the possible perturbation of the ozone layer by CO 2 and chlorofluorocarbons (CFC's). Four experiments are described: a control run; a run including increasing levels of CO 2 up to 625 ppm; a run including a source of chlorine compounds from the CFCs; and a run to investigate the coupled perturbation due to both CO 2 and the CFC's. The dynamical and chemical behaviour of the runs is described. The control run reaffirms the conclusions of earlier experiments with this model (Harwood and Pyle 1980) that the summer stratopause is very close to radiative equilibrium. The strength of the polar night jet is also discussed. The perturbations due to CO 2 and the CFC's have opposite effects on ozone with increasing CO 2 producing an increase in column ozone which is greatest in high latitudes. The coupled perturbation is not a linear combination of the two individual experiments. This is investigated in terms of the photochemical scheme used. The reduced temperature dependence of the ozone concentration when chlorine compounds play a significant role is shown to produce the non‐linearity.